Although the activity per se of an enzyme which synthesizes core 3 sugar chain (N-acetylglucosaminyl β1,3N-acetylgalactosaminylα1-R; GlcNAcβ1-3GalNAcα1-R), which transfers N-acetylglucosamine to a non-reducing terminal of N-acetylgalactosaminyl group is known, the enzyme has not been isolated or identified. Therefore, to prepare or produce the core 3 sugar chain structure, it is necessary to chemically synthesize the structure, isolating the structure from a biological component or to synthesize the structure enzymatically using a tissue homogenate. Further, it has been reported that although this enzyme activity exists in normal digestive tract, the activity is lost in established cell lines originated from digestive tract. This means that although the enzyme exists in normal digestive tract, the activity of the enzyme is thought to be reduced in abnormal tissues such as cancers and digestive tract polyps. Therefore, to examine the change in the expression amount of the enzyme or to examine the core 3 sugar chain is important for diagnoses and therapies.
By isolating an enzyme having an activity to transfer N-acetylglucosamine to N-acetylgalactosaminyl group through β1,3-linkage, and by characterizing the structure of the gene, production of the enzyme by genetic engineering process and diagnosis of cancer and the like based on the gene may be attained. However, the enzyme has not yet been purified or isolated, and there is no clue to the isolation of the enzyme and identification of the gene. As a result, an antibody to the enzyme has not been prepared.